inscatolati - Get out of the box! :)
slapcat shows an entry that cannot be found if accessed directly by cn
[50]
Let's say you have a LDAP database served by openldap. Let's say that your applications keep querying this database to provide authentication / addressbook / whatever. At a certain point in time, slapd starts telling you that a certain entry does not exist when you try to fetch it directly, but, it does show up when doing a 'sub' search or using slapcat.
This is usually a symptom that the index of the ldap database is corrupted. You can regenerate it by using 'slapindex' as root. After running it, remember that if you are not running slapd as root, you should fix the privileges of the files (chown slapd *).
You might also want to regenerate the database, something like slapcat > /tmp/backup; rm -rf database/files; slapadd < /tmp/backup or similar.